1. Field of the Invention
The present invention relates to a method of isolating nucleic acid using a material containing an amino group and a carboxyl group and which is positively charged at a first pH.
2. Description of the Related Art
Conventional methods of isolating nucleic acid using pH-dependent ion-exchange matrices include U.S. Patent Publication No. 2001-0018513, which discloses a method of isolating nucleic acid using a material having an ionizable group, wherein the ionizable group is positively charged at a first pH so that the material can bind with nucleic acid, and the material releases the bound nucleic acid at a second pH which is higher than the first pH. Examples of the material having an ionizable group include N-2-acetamido-2-aminoethanesulfonic acid (ACES), N-2-acetamido-2-imidodiacetic acid (ADA), N-trihydroxymethyl-methyl-2-aminoethanesulfonic acid (TES), trihydroxymethylaminoethane (Tris) and the like. Furthermore, U.S. Pat. No. 6,310,199 discloses a method of isolating nucleic acid using a pH-dependent ion-exchange matrix comprising a silica magnetic particle and a plurality of first ion exchange ligands. Each of the first ion exchange ligands contains an aromatic hydrocarbon ring, a spacer covalently attached to the aromatic hydrocarbon ring, and a linker comprising a linker alkyl chain covalently attached to the silica magnetic particle at a first end of the chain and covalently attached to the amino terminus of the spacer at a second end of the chain.
However, despite the prior art methods described above, there is still a demand for a material having an ionizable group that can bind with nucleic acid at a high rate, and can release the bound nucleic acid with high efficiency upon an increase of pH. Thus, the inventors of the present invention have searched for a material which can bind with a nucleic acid at a higher rate to adsorb the nucleic acid rapidly, and can release the bound nucleic acid with remarkably high efficiency upon an increase of pH, and found a bifunctional material containing both a carboxyl group and an amino group, thereby completing the invention.